I'm looking into building a small wind turbine out of a bicycle wheel. They are light, durable, and don't take much effort to spin, which means they'd be good for generating power even in low winds.

First, forgive me for my limited understanding of power. Watts, amps, volts... I'm not sure which exactly does what, and what limits are acceptable for a generator/motor or for providing to the power grid.

I understand that the goal is, by harnessing the wind's energy to spin your blades on the bicycle wheel, it then spins a magnetic generator/motor, which produces electricity you can then feed into a battery, or back into the power grid. What I'd like to do is feed right back into the grid. I have read that you want a DC motor to hook up to the spinning turbine (some people say a magnetic generator), and that the more rpm's your turbine causes the motor to spin, the more it feeds into your power grid. I believe that the motor sends voltage into the grid, correct me if I'm wrong! It's recommended to get a motor that can handle over 10 amps as well. Apparently if a turbine spins too fast, it can burn out a weak motor. We need a motor small enough that even a bicycle turbine will spin up enough so that it produces electricity, but it has to be able to handle higher speeds in case of a storm, without burning out. I'm not sure what motor is appropriate for this application.

I'm not sure how to hook this into the power grid. I saw something about an Amp Blocking Diode- is this so you don't feed too much into the grid at once? And an inverter is said to be required to hook a turbine into the grid too. Again, I'm not sure what kind to get.

Also, obviously the rpm's will vary a lot with wind speed. How would the grid handle receiving 0.5 volts in light wind, and say 12 volts in a storm? Can it even accept the power as low as .5V from the turbine? I don't think a bicycle turbine would produce a ton of electricity, but it's a project, a learning experience and I want to see if it's practical and would actually work, even if it only powers one light bulb.

When the zombies come, I'll need a way to charge whatever gizmos I have with me, and a bicycle-sized turbine with all the necessary electrical equipment could easily be modified to charge a car battery. The contraption could sit in the back of a pickup truck if I need to be on the move.

But for now, I just want to build this and see what it can put out. I found an equation online. Power = .5 x 1.23(air density) x area of blades (or bicycle wheel in this case) x wind velocity cubed. Area needs to be in meters. A foot is 0.609 meters. Let's assume this thing is 30% efficient, as the max efficiency for a turbine is 59.26% and there's no way I'm achieving that.

So assuming a 1 foot blade(from wheel hub to tip of blade... pi times r^2 for area) and 10mph (4.5 m/s... everything is metric) winds, we get 0.5x3.14x.3045^2x.3x4.5^3. Or 4.89 watts, assuming this is correct. But in 20mph winds, it's 39 watts. And if the blades are 3 feet in diameter, it can produce 88W in 20mph winds! Remember, you cube the wind speed, and also the blade length gets squared. Therefore increase in power output is not linear with wind speed (or blade length) increase, as you can see! I don't know how this all relates to volts and amps though... if I'm producing 4.89W, that's gotta be pretty low voltage right? Would this low voltage power be usable or transferrable to the power grid, or does the grid need something at exactly 12.0V, or what?

What I need now is to figure out which motor/generator to use, which inverter, and how to hook this up to the power grid. I understand I may need a license to use one of these on my property or hook it into the grid, or an actual electrician to set it up. I'm not attempting this by myself, don't worry. I simply want to know how it would work, and if I can get it to make sense I'd love to do it.

Thank you for your consideration!

Wow that's a lot of information. I wish I was smarter and could help, unfortunatly I'm not the person to help you. However if you get this going please keep us updated as I am interested in your idea! Good luck!

It's usually very hard to actually sell power back into the grid as an IPP (Independent Power Producer), but usually easy to locally create some power and use it in your home and reduce your energy bill.

I used to work for a renewable energy company and did some remote village electrification in South America in the mids 90's.

I would suggest that you check out the Home Power Website and get a subscription to thier magazine and you will learn a lot: http://www.homepower.com/home/

The turbine that you describe built from a bike wheel is unlikely to ever be a commercial quality unit, but you should be able to charge some batteries and have some fun. The hight of your tower will be critical as the power from a wind turbine is a function of the wind speed.

Thanks guys! Good link. Lots of info.

Apparently most wind turbines produce wild 3-phase alternating current, which must be rectified to DC current so you can feed it into a power grid. This is what an inverter does. The current is 'wild' because Voltage and frequency will vary with wind speed.

So once the supposed bicycle turbine is hooked up to a magnet alternator/motor/generator (or whatever you want to call it, I guess...) the wild power it provides is fed into said inverter.

I guess I need to find an inverter that would work for a small application. I'd guess most have a huge capacity and cost thousands of dollars. I also need to find an appropriate magnet alternator.

My recommendation, forget about selling power back to the utility for now. Most states don't require the utility to buy it back from individual producers, so they don't. I don't blame 'em for this, I wouldn't wanna mess with it if I were Florida Power and Light or Comm Ed either.

If you follow this musing you're gonna learn a lot about physics including electrical theory and fluid mechanics real fast. Think about it like this, you've already learned about the practical application of kinetic energy equations and the existence of AC and DC.

Three considerations are of importance for a commercial installation:
1. Tax Credits
2. Distance from population centers / existing infrastructure
3. Constant steady wind
(just about in this order too)

You're in a different boat, as it seems like this is just a project to prove concept. You may not have to worry about economics or transmission lines. But, if you don't live on a bluff or in a gorge you might be real disappointed in the results. The amount of time most places in this country have a steady wind that will make enough juice to worry about is pretty low. But, assuming you and the north wind gods are tight...

For a someone who doesn't have access to a full machine shop and a cadre of engineers, the design has to be simple and the parts readily available off the shelf. Seems for the hobbyist the best bet is a vertical wind turbine (google for pics). I've seen them formed from plywood and fiberglass. I'd look into using regular automobile wheel bearings for the rotational elements. Height is another consideration. Most roofs were not designed to support any more load then they already have. Then electrical generation... I've heard tell of people having moderate success with regular automobile alternators, but keep in mind that the most efficient speed for the alternator and the most efficient speed for the wind-rotating portion are nowhere near the same. This means a series of reduction gears will need to be employed. For this I recommend bicycle cogs and chain-rings. You still only have a relatively unreliable source of low voltage DC. Now you need to store the energy you've created and get it into a useful form (either a steady 13.8 Vdc or 120 Vac), possibly a battery bank with an inverter.

I don't wanna talk anyone out of a fun project, but there is a reason most people have gasoline or diesel generators as their backup power.

Thanks nateted 4. I understand what you're saying- I wouldn't expect a homebrew turbine to produce enough to sell back to the grid. I figure even if it's only a few watts at any given time though, it could feed a small percentage of my house's needs, even if it only saves pennies a year. I think it'd be a really neat project to hook up even if it the energy produced doesn't ultimately save me on my energy bills.

I'd like to build it without a battery and just hook it right up, which sounds cheaper. Plus, charging batteries makes you lost a good amount of efficiency. I have read the vertical turbine DIY's and they look pretty cool, but they don't produce as much in the end. It would be easier though, because with a bike wheel on a pivot, the pivot could turn 360 degrees many times a day as it follows the wind, and whatever wires I have hooked up to carry the current produced might twist and break. Any ideas on how to prevent this?

They make connectors to solve exactly this problem:

"http://www.mercotac.com/"

If you google "slip ring connector" there are also DIY versions.

As to paralleling your home-made juice with the grid, this install has to be professionally done to protect the safety of the electrical linemen. The Utility will demand a commercial rig designed specifically for this purpose. The cost of this will blow any savings of a bike wheel turbine out of the water.

I'll trust you calculation of 5 watts at 10mph. To give you an idea of how little energy that really is, five watts is barely enough energy to light an led lamp and a weather radio.

Wow... um... ok, where to start...
Start with the standard disclaimer: I am no expert. Take this for what it is: free advice on the internet. Always consult a professional before you do something that may or may not be stupid. If you hurt yourself, your home, your loved ones, your hated ones, your pets, grand pets, neighbors or whatever because you followed free advice on the internet. It's your problem. If I missed something, please correct me. I like to know when I'm wrong so I don't do something stupid as was previously mentioned.

Lets start with grid buyback. The grid is AC (not DC as was previously mentioned). Having the power company buy back power you generate is called net metering. Net metering is available in many states and is being pushed in many more. It's not difficult at all (in the US anyway). The grid companies love the fact that you're helping to alleviate the strain in the grid. In fact, this kind of interactive grid is key to many emerging green power trends.

Wind turbines... are easy enough to build. Take a look here, here, and here for just a few examples. The "wild" power that your system outputs should go to a quality grid interactive or independent regulator/charge controller attached to a battery bank (for power in a grid down scenario) or not (if you just want to offset your energy costs). The battery bank option is DC and can power a separate DC system in your home. Alternatively you can run an inverter on the batteries to create AC (what all your normal stuff runs on). Using DC directly is the most efficient option, however, the longer you run you DC lines the more power you will loose. Keep your runs short. This is why the grid is AC.

Longer blades are better as they harness more wind. If you're looking at interesting options, look at a wind turbine built out of old barrels (VAWT?). A wind turbine will not output 3 phase power unless the coils are set up to do so (most aren't). Don't bother with a 3 phase setup. It's generally more trouble than it's worth. You cannot connect anything directly to the grid unless you are a licensed electrician. If you mess with the grid you stand a very good chance of killing yourself or someone else. Have the electrician install the regulator/charge controller and you can hook items up to it (within reason). You need to do significantly more research before you reach this stage, though.

Finally, is wind even worth while? Look at this map to see. Raw data is available there too.

ETA: http://thesurvivalpodcast.com/forum/ind ... board=19.0 <- Some more info over here.

I would suggest you either study the Honeywell low wind turbine or get yourself a WindBlue low wind alternator.

Sorry to burst your bubble, and with all due respect, to sell your power back to the power company, you first have to produce more than you are using and also require a grid tie inverter which cost between $2,000 and $4,000. A homemade wind turbine, if built right and with enough wind with the right motor like the Windblue alternator or an Ametek 30 will produce between 200-600 watts of power. That equates to about $0.24 off your bill if you follow the national average of power conumption in your household.

So... building it to sell your excess power isn't a very good idea. But if your intention is to recharge an emergency battery bank then you might be on the right path.

If you want more information on this then PM me. I am happy to offer your some suggestions. I've been studying this hard for a few months now.

Meanstreak,
It must vary based on your area.

MA law from National Grid's net metering page:

It further goes on to say...

So no, I don't need to produce more power than I use to sell back to the grid. At least not with my grid provider (national grid). This is why it's so important to check your area specifically. Who's your provider?
As an aside, I may not make money, but I'll certainly offset my bill. It may not make financial sense, but that's something that has to be taken on a case by case basis as well.

ETA, Nice wind alternator!

Don't worry, I don't have a bubble to burst! I am fully aware of how little a homebrew would produce. I don't care of it saves me $0.01 (we use about 400kWh/month, or a little over 13kWh per day, which comes to about $50/month); it's more of a project than anything. I want to see how much of a challenge it is to build one, and how much the parts to make it work with *reasonable* efficiency would cost.

That's a good attitude to have with a project like this

I'm sure it varies from area to area, but my point was that the money you get back is little. Believe i would love to tie my solar panels into the grid but the cost is prohibitive.

What about these cheapo grid tie inverters (250W or whatever) I see on Ebay? They can't have as high an efficiency as the several-thousand-dollar models, but why wouldn't they work for a small solar or wind setup?

You still have to pay a licensed electrician to hook it up. If the ones on ebay have a good rep, you might as well get one. But if you can't find a bunch of corroborating reviews on those, buy a good quality one (not necessarily expensive, but good grid tie charger/inverters usually are). Unless you know an electrician that will hook it up for cheap.

I noticed that a lot of these cheaper 250-300W Ebay inverters say 10-28V. Others are 14-28V, etc. One also says there's a 30W minimum to start up (the 10-28V one). All of these inverters must have some sort of lower limit. It would be nice to find one with a very low start up wattage/voltage... another one, which mostly talks about being used for solar purposes, says it has a minimum of 8W to start up for instance.

Quick thought... for an inverter to send power back to the grid doesn't it have to be doing so at greater than 12V? And do these things have a blocking diode built in, so if it's only making 8V, the grid isn't sending power back through the inverter?

I'm also curious what makes electricity provided by your inverter go directly to your home appliances as opposed to through your meter. There's gotta be some mechanism whereby your appliances get "first dibs" on your wind/solar power sent back into your home, as opposed to it getting sent back out into the world, through the meter and you getting paid for it... but how? I mean, it'd be equivalent both ways. Say your appliances use 1000W all day every day and your inverter is providing 200W. Either those 200W go directly to your appliances, so you're only drawing 800W from the utility company, or you're drawing 1000W from them and sending 200W back... which is the case, and why?

The descriptions also seem to imply that you plug your solar panels or whatever into the inverter, then plug the inverter into a standard AC electrical outlet in your home. The inverter sends whatever it receives from the panels directly into the power grid through an outlet. ...I guess I figured it would be harder than that, that you'd have to hook an inverter up to the meter or some funky fuse box or something. Is it really this easy with these small inverters?

So, as I understand it, you need to produce more than 12V to feed it into the power grid. Therefore, the goal would be to build a turbine that could produce 12V at low wind speeds... obviously, a bigger turbine will be better for this. But the motor should produce high voltage at low RPM's. The Ametek motors are good for this I hear...

Wow, lots of great questions... Again I'm no expert but...

First off, it's a grid tied inverter, not just an inverter. There's a big difference. You can get an inverter from Home Depot that you clamp to your car battery to run a light off of for cheap. That's not what we're talking about when we say a grid tied inverter.

Check out Outback Power Systems (their forum, wiring diagrams). Here's a block diagram overview from Outback.


You do not just plug an inverter into your home power line for the same reason you don't do that with a generator. You could kill someone working on the line or overload that particular circuit.

Take a look at this overview, do some more googling (try "introduction to alternate power" or "How does a grid tied solar system work") and keep asking questions.

I believe the inverters i see on eBay are just inverters. I know they say "Grid tie" inverters but they don't look like it. They actually look just like simple inverters that you could buy from Walmart. I would buy one of those with caution.

If a 13 year old boy in Malawi can do it, so can you. You can learn more about his incredible story here: http://news.bbc.co.uk/2/hi/africa/8257153.stm

You have received some great feedback. Stop thinking about it and start doing it. The journey will be a reward in itself.

The little cheap inverters are the type I have in my van. If you're running home equipment, don't make my mistake: don't get under 1kW. A lot of devices draw more on startup and that trips my 500W out.

The higher-power devices though have a higher start-up wattage requirement. For instance a grid-tie inverter capable of 1000W might not even start up unless my (hypothetical) turbine produces 30W.

The inverters I'm talking about are also for taking wild AC power from a turbine or hydro, or what-have-you, and converting it into a form it can inject into your home power grid. I don't think it's the same kind you plug into a cigarrete lighter... plus, the inverters have a blocking diode so if the turbine isn't producing hardly any electricity, this will prevent the inverter from drawing power from the wall (which has a higher voltage than the inactive turbine's generator/motor is producing) and spinning the turbine. As I understand it, power flows only from the turbine to the wall, providing it is spinning fast enough. If it's not, then no power is sent into your power grid.

I could have this wrong. If I do please let me know!

Grid tie inverters in theory do the same things as a cigarette lighter type of inverter - the convert DC power to AC. The difference is in their purpose. Grid tie inverters are usually built with a shut off. When the grid goes down they shut off so you don't continue powering the grid. That could potentially hurt an electric worker trying to fix the problem. They're also designed specifically to be plugged into your power grid while the smaller inverters (cig style) are not.

Grid Tie inverters are expensive because of the hype right now. Here are some of the cheapest Micro Grid Tie Inverters i have seen.

if you want to build your own wind generator you should check out this site: http://www.otherpower.com/otherpower_experiments.html

You needn't reinvent the wheel, in this case the bicycle wheel wind turbine. Ted Baer designed and built a great one about 4 years ago. You can find instructions for it at: http://www.instructables.com/id/Ted-Bae ... -Windmill/
Hope this helps.